Faint Line on Drug Test: Is it Positive, Negative, or Invalid?

A Very Faint Line on a Test Strip as a Result of THC Urine Drug Test


Quick answer: A faint line on a drug test is deemed a NEGATIVE TEST RESULT, which suggests that the test did not discover any trace of that substance above the test’s cutoff level.

When you see two lines (no matter if it's a very faint line on a drug test for THC or a dark line), it means that the result of your test is negative. If you’re using an Exploro® THC test and see that the bottom line shows up very faint, that means that the concentration of THC metabolites in your body is somewhere around 50ng/ml (which is the cut-off level of the Exploro® THC test strips). 


Keep reading to learn:


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What Do "C" and "T" Stand For on a Drug Test?

The C stands for the "Control" line in a THC rapid drug test. The T stands for the "Test" line.  The Control line indicates that the gadget is working properly, while the Test line indicates that no drugs are present.

You can see the different results of a THC urine drug test below. If there is only one line in the "C" area, the test is POSITIVE. The "T" area with one line (or no line at all) is INVALID. Then we have the infamous “faint” line.

           Positive Result for Exploro THC Urine Drug Test     Invalid Test Result for Exploro Urine THC Test Strips Kit          

How Faint Can a Line Be on a Drug Test & What Can it Look Like? (+ pictures)

On a THC drug test, for example, a faint line can appear as a blurred, pinkish line in the "T" region with a line on top in the "C" area. This is still a NEGATIVE result, even if it's hardly apparent. The most typical reason for a weak T-line is that there is drug present in the sample but not enough to give a positive result beyond the test's cutoff. In the case of Exploro® THC test, it’s 50ng/ml.     

Negative Test Result for Exploro THC At-Home Test Strips

Over-interpreting a faint T-line is not the best practice. A faint T-line with even a smidgeon of color is always considered as a NEGATIVE result. If you have a faint line on your pre-employment drug test, you are still regarded to have passed.

Drug tests are used to identify whether or not a specific substance (in most cases THC) is present in a sample by looking for the drug(s) and their metabolites. Rapid tests are commonly used to determine whether a substance is present in the body in a short period of time. THC metabolites are detected in the form of negative or positive results in at-home tests, but the quantity is not shown.

Here are some examples from Exploro® customers and their tests with faint lines. 

Negative THC Test Result With A Faint Line Performed on Exploro Highly Sensitive THC Test Strip For Home Use  Review About The Accuracy Of Exploro At Home Marijuana (THC) Test Strips Kit Showing A Faint Line  

Positive Feedback From Exploro Customer About THC Testing Strips With a Faint Line in the T Area  Very Very Faint Line on a Negative THC Urine Test Strip By Exploro Products

Faint Line On THC Drug Test Produced By Exploro Products  Faint Line on an Exploro THC Drug Test

Pictures source: Exploro® customers 

What Can Cause a Faint Line on a Drug Test?

For those donors who have never smoked, THC tests may show faint lines, which can be concerning. This occurrence can be attributed to the components of the test, as well as interactions between more natural substances and the urine sample, making THC tests more prone to producing faint lines. Faint lines on drug tests can show up due to the following reasons:

  • Not leaving the test strip inside a urine sample for long enough.
  • Not having enough THC in the bloodstream to cause a fully positive result, but enough to leave a small trace, causing a faint line.
  • Chemical imbalances or dilution of the urine sample (for example, drinking too much water before doing the test).
  • Using an expired test. Make sure to always check the expiration date.
  • Taking over-the-counter medication that is chemically equivalent to the drug being tested.

Every substance has a baseline (cutoff) that shows up on any drug test. The cutoff level for Exploro® is 50/ng per ml, so if you test below that, you are always negative. There is always a TINY amount of wiggle room in any drug test because different tests may have different cutoff levels.  If your test shows a faint line, however, your employer cannot fire you for failing a drug test because the result is still considered negative. However, it’s possible that your employer will ask for a confirmatory lab test

How to Prevent Faint Lines on Drug Tests

Although you may encounter faint lines on a drug test, you can always take steps to ensure that your results are as precise as possible:

  • During testing and storage, keep an eye on independent factors, like temperature.
  • At the 5-minute point, consistently read the results, but disregard any results after the 8-minute mark.
  • Throw away any opened and unused tests as well as any expired tests.
  • Ideally, conduct the test first thing in the morning, before drinking any water.  
  • If necessary, submit a list of all drugs, supplements, and energy drinks you took prior to the test.

The Bottom Line (Pun Intended!)

Regardless of how light they are, faint lines in the test zone of the sample are declared negative. Most people use THC testing strips at home in order to find out whether or not the drug is present in the body below the cutoff level (this may differ from test to test).   

A faint line on a drug test is common and will always mean it is a negative result, no matter what. If you keep getting faint lines or no lines on your test, make sure to check the points above. Otherwise, try again with another test (without drinking water) and see what result you get.


What does a very very faint line almost invisible mean? Is it positive?

No. It is still a negative result even if the second line is super faint. ANY line in the “T” area, indicates a negative outcome. The tests don't check for the number of drugs in your body or urine; they merely check for the presence.

Will I pass a lab test with a faint line? 

The cutoffs for at-home tests are frequently higher than for lab tests. The laboratory tests however are more precise. If you have a few days until a lab test for marijuana, the faint lines are unimportant. The reason is, that if there is a line, it means the result is negative. 

TIP: In the days before your drug test, try to avoid eating a lot of sugar or carbohydrates, or try one of these THC detox methods. Marijuana lingers in your fat, so if you're overweight and out of shape, or if you have any health problems, getting the drug's metabolites out of your urine may take longer.

What if I get two faint lines on my drug test? 

Your test is negative. If two lines show up even if faint, it still means it’s a negative. The cause of faintness can be a range of reasons, but no matter what, the result does not change.

Is it possible to get a faint line on a 7-panel drug test?

Yes, a faint line can appear on a 7-panel drug test. As each drug has its own strip on a 7-panel test and the results are individual to each, you can see where you tested negative (with a faint line in either the “T” or “C” area) or positive (only one line in the “C” area).

Is it a positive result if only the Test line ("T") appears?

No. If the Control line ("C") doesn't show up, the test is invalid. Only the Control line ("C") must be visible for a positive test result.

Why isn't the top line ("C") on my test strip visible?

If the Control line ("C") does not appear on your THC test strip, make sure that your test isn’t expired, the temperature of the urine and room is not too cold or hot, etc. Then, do the test again. In some cases, you might not see the C-line because the test was flooded by too much urine or the test was added to the urine too quickly.

Why do I get both positive and negative results in such a short time? 

In rare situations, contradictory test findings can appear within a short period of time (even within the same day). This often indicates the THC content in your body is roughly around 50 ng/ml (the cutoff level of Exploro® test strips). 

My test strip is negative after 5 minutes, but it is positive after 20 minutes. Why? 

When testing your urine for THC, make sure you follow the directions that came with the product. Ensure that you verify your test at exactly 5 minutes and don’t interpret the results after 8 minutes. The chemical reaction becomes unstable after 8 minutes, and color changes may occur.



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What does it mean if the test show up as a C does that mean didn’t pass the test?

Dianne Harr

I smoked marijuana 3 days ago. Why is the test showing a faint line? I smoke daily usually


After 3 consecutive faint line urine dip drug test results , each done a week apart, when can I expect to see a darker line?


Aaahhhhh….so, this is how drug tests are conducted? Thanks for sharing this literature!

Ntensibe Edgar

Thank you for the clarification. Great post.

Jen Schreiner

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